Centrifugally controlled slip switch



1931- G. H. WHI TTINGHAM 1,837,303

I CENTRIFUGALLY CONTROLLED SLIP SWITCH Filed Oct. 25, 1930 2 Sheets-Sheet 1 Jwuenkoz n; M W W attozmq Dec. 22, 1931. G. H. WHITTINGHAM CENTRIFUGALLY CONTROLLED SLIP SWITCH 2 Sheets-Sheet Filed Oct. 25, 1930 z E g.

v llllllllllk Patented Dec. 1931 UNITED STATES- PATENT OFFICE v enema WHITTINGHAK, OF BALTIMORE, MARYLAND, ASSIGNOR TO MONITOR CONTROLLER comm, OF BALTIMORE, MARYLAND, A CORYORATION OI KABYLAND CENTBIFUGALLY CONTROLLED SLIP SWITCH Application filed October 25, 1980. Serial No. 491,274.

This invention relats to switch operating mechanism adapted for applicatlon to reversible shafts, the purpose of the invention be-- The invention is adapted particularly for use as an aid in the sto page of induction motors. Thus, where a ynamic braking action is applied to an induction motor of the wound-rotor type, to stop the motor by temporarily reversing the current phases in the rotor circuits, in well known manner, the II mechanism of the present invention ma be used to cause the interruption of the bra ing circuit at a predetermined time before the rotor of the motor comes to rest. In the accompanying drawings, which illustrate the invention,

Fig. 1 is a side elevation of the mechanism embodying the invention, partly broken away, the casing being shown in vertical section and the parts being shown in normal positions;

Fig. 2 is a top plan view of the switch;

Fig. 3 is a top plan view of the switch 6 erating mechanism, the shaft being part y broken away and the parts being shown in 80 normal positions;

F Fig. 4 is a section on the line of 44 i 3; a i

i 5 is a section the same as in Fig. 4,

but s owing the relation of the parts when" 85 the motor shaft is turning;

Fig. 6 is a section on the line 6-6 of Fig. 1; Fig. 7 is a side elevation of the movable friction disk;

Fig. 8 is a perspective view of one of the links connecting the centrifugal governor with the sliding cone;

Fig. 9 is a side elevation of the cone; and,

Fig. 10 is a similar view of the sleeve upon which the various parts are mounted.

' Referring to the drawings a indicates a casing, in the opposite sidesof which are bushings 1 which form bearings for a shaft 2'which extends through the casing and is rovided at one end with a driving pulley 3. pon the shaft, and rotatable therewith, is a 7 pair of stationary coritacts 12 and 13, and the centrifugally operated device b and a friction device a which is frictionally clutched tothe shaft and released therefrom by the operation of the governor. Above this mechanism a switch at is mounted on a base or panel 4, of insulating material, which is supported by brackets 5 on the side walls of the casing. An arm 6 projects upwardly from the friction device through a slot 7 in the switch base and into a fork 8 at one end'o f a switch lever 8, which lever is centrally ,pivoted on a post 9 and adapted to swin parallel with the top surface of the base. pon the end of the lever opposite the fork 2, contact members 10 and 11 are loosely pivoted u on a pin 8 which extends through the ever. These contact members are alike, each U-shape in transverse section and having contact buttons on their outer edges.( Thus, the member 10 has contact buttons 1'10 adapted to engage a member 11 has contact buttons 11' adapted to engage a pair of spaced stationary contacts 14 and 15. The stationary contacts, being arranged on opposite sides of the lever, as shown, serve as sto s to limit the movements of the lever,an each contact member on the lever is adapted to electrically connect or bridge one pair of stationar contacts.

As shown Figs. 1 and 2 of t e drawings a light spring 16 is connected to a stationary pm 17 'near one end of the slot 7, and to an eye18 on one side of the switch lever between its pivotal point and the end of the lever which carries the contact members, and this spring normally holdsthe lever in the posit1on shown in full lines, with its contact member 11 against the stationary contacts 14 and 15. If it is desired to have the contact member 10 normally held against the stationary contacts 12 and 13,. the spring will be removed from the pin 17 and eye 18 and connected to a pin 19 at the'opposite end of the slot 7 and to an eye 20 opposite the eye 18. b In the drawings, wires 21 and 22 are shown connedted to the contacts 12 and 13, and these ma lead to a relay or contactor which contro s the braking circuit of a motor which drives the shaft 2. :This circuit is normally open at said "contacts, but is closed when the lever is moved into the dotted line position by the movement of the arm 6.

The arm 6 projects radially from a friction disk 23, of carbon-graphite compound, which is loosely journaled upon one end 24 of a sleeve 0 which is secured to the shaft 2 by a set screw 25. The disk 23 fits snugly within a peripheral metal band 26 and the end of the arm is threaded into this band and extends into the disk, thereby locking the parts to gether. A metal washer 27 is secured tightly to the sleeve at one side of the friction disk and a washer 28, at the opposite side of the disk, is keyed to the sleeve so as to rotate with it, but is movable longitudinally of the sleeve into and out of engagement with the friction disk. As shown, the sleeve has a longitudinal slot 29, and a tongue 28 on the washer pr rijficts into this slot.

.e sleeve c has a cylindrical part 24: at one end upon which the friction disk and washers are mounted, a central cylindrical portion 24 of larger diameter, and the end portion 24 is rectangular in cross section and of larger diameter than the central portion.

A shallow annular groove 30 is formed in the end of the central portion, adjacent washer 23, and an endless helical spring 31 rests normally in this groove.

A block f, having a central bore, is slidingly mounted on the part 24 of the sleeve and has a conical end 32 adapted to extend within the annular spring and force the latter out of the groove and against the washer 28. As the block or sleeve f is forced toward the washer the spring expands radially and. presses evenly against the washer along a circular line so that the inner face of the washer bears with equal pressure at all points against the friction disk. The tension of the spring on the tapering surface of the block or sleeve f tends to force the block away from the washer toward the end 24? of the sleeve. When the block is moved to the latter position the spring contracts and rests in the groove-30 and the lateral pressure against the washer 32 is relieved, as also the pressure of the washer against the friction disk.

The block 7 rests against the part 2 1 of the sleeve when the shaft is stopped, as indicated in Figure i, and it is automatically forced into position to expand the spring by the centrifugal governor h when the shaft is rotated. This governor comprises two similar flat weights 33, these weights being held parallel. with one another and spaced apart by osts 34% which are riveted to the weights. he weights have central threaded openings 35 and the posts are diametrically opposite these openings. a s 36, thr aded into the openings, have i'J-lilt .es 3? en ti inner ends which enter a onlar part bhre 38 in the rest 24 of the sleeve This bore extends through the sleeve at right angles to two of its sides and in line with the axis of the shaft 2. Be-

tween the squared portion of the sleeve and the weights are arranged links 39 one of which is shown in Figure 8. Each link has a pintle 39 at one end and a slot 39* at the opposite end. These pintles extend into openings 40 in the weights near the axis of the weights and the slotted ends of the links enage pins 41 on opposite sides of the sliding lock or sleeve 7.

It will be evident that when the shaft is rotated above a certain minimum speed the weights will turn about their axis and the links will be moved to press the block 7 toward the friction devices. The spring 30 is expanded by this movement and rides up on the conical part of the block. As the shaft speed slows down, the pressure of the spring againstthe conical end of the block forces the block toward the axis of the weights and-the links rock the weights to their normal posi-- tion, shown inFigures 1 and 4, before the shaft stops.

To limit the movement of the weights and avoid shock, when the shaft is started, a yielding stop is provided on the part 2% of the sleeve. This stop consists of a rigid metal strip 42 and a resilient metal stri 1:3, both secured at one end to the part 24 y a screw 44, and both bent outwardly from said part, as shown. The projecting ends of the strips lie in the path of movement of the adjacent post 34, with the resilient strip spaced from the rigid strip so that it will cushion the blow of the post as the weights swing outwardly and before they are arrested by the more rigid strip.

The operation is as follows: The motor to be controlled, or some part driven by the motor, is belted to the pulley 3 so as to drive the shaft 2 at a moderate speed when the motor is in operation. If the shaft is to turn in the direction of the arrow, Figure 1, the spring 16 will be connected as shown in Figure 2 and the contact member 10 will be normally held away from contacts12 and 13 and the arm 6 of the friction device will be held in theposition shown in full lines in said figure. When the motor starts, the rotation of the shaft 2 will cause the centrifugal device to swin about its axis from the position shown in igure 4 to the position Figure 5 and the sleeve or block f will wedge the helical spring out ofthe groove 30 and against the washer 28, which latter will bear against the friction disk with sufficient force to rotate the latter and the arm 6 will swing the switch arm 8, against the tension of the spring 16, from the full line position in Fig ure 2 to the dotted line position, wherein the contact member 10 abuts against the stationary contacts 12 and 13 and electrically connects said contacts. The friction device will hold the switch in this closed position as long as the shaft is driven in the directionindispeed. When the motor is slowed down, as by applying a braking current to it, the shaft 2 slows down and the pressure exerted against the block f by the centrifugal device de- 5 creases. This permits the spring 31 to contract, and in contracting its pressure against the conical surface of the block forces the latter away from. the friction device, and V the block, acting through thelinks 39 rocks the weights of the centrifugal device to normal position just before the shaft 2 stops. As shown in Figure 4, the spring 31 contracts into the groove 30 immediately before the shaft stops and the pressure of the spring against the washer 28 is relieved so that the latter no longer bears against the friction disk. As soon as the pressure of the'washer against the disk is sufiiciently relieved, the

spring 16 moves the switch lever 8 and the 20 arm 6 of the friction deviceback to normal positions as illustrated in full lines in Figure 2, and the circuit is opened at the contacts 12 and 13.

Thus it will be seen that the circuit which is held closed while the motor is running normally, is opened immediately before the motor comes to rest.

If it is more convenient to have the shaft 2 turn in the opposite direction from that in dicated by the arrow in Figure 1,-or clock wise, as viewed from the pulley end of the shaft, the spring 16 will be shifted so as to connect the eye 20 on the lever with the stationary pin 19, and the circuit wires 21 and 22 will be transferred to the contacts 13 and 14. The switch lever will then normally lie in the dotted position Figure 2, with the switch open at the contacts 14 and 15, and when the motor is started the friction device will move its arm 6 and the'switch lever to the full line position wherein the circuit will be closed at the contacts 14 and 15 by the contact member 11. When the motor slows down,

and just before the shaft 2 stops, the friction device will be released and the spring on the switch will return the switch lever to the dotted position.

What I claim is:

1. Circuit controlling means comprising a shaft, a friction member rotatable about the shaft, a switch operable b said member, a device rotatable with the s aft and adapted to frictionally engage said member, and centrifusally-operated means adapted to force said evlce into frictional engagement with said member when the shaft is rotated above a certain low s eed and to release said device when the sha slows. down and before it stops. I v

2. Circuit controlling means comprising a shaft, a friction disk rotatable about the shaft, a switch operable by said disk, a washer rotatable with the shaft and adapted to frictionally engage the disk, a centrifu al' governor and means operated thereby or er rotatable with the shaft and movable to frictionally engage said 'disk, a spring adjacent the washer and centrifugally-operated means adapted to force said spring against said washer when the shaft is rotated and to release the pressure on the spring when the shaft slowsdown and before it stops.

4. Circuit controlling means comprising a shaft, a'f'riction disk rotatable about the shaft, a switch operable by said disk, a washer rotatable with the shaft and movable to frictionally engage said disk, an annular helical spring surrounding the shaft adjacent the washer, a member slidable longitudinally of the shaft and having a conical surface adapted to enter and expand said spring radially and force it against the washer, and a centrifugal device adapted to move said slidable member into position to expand the spring when the shaft is rotated.

5. Circuit controlling means comprising a shaft, a friction disk rotatable about the shaft, a switch operable by said disk, a washerrotatable with the shaft and movable to frictionally engage said disk, an annular helical spring surrounding the shaft adjacent the washer, a member slidable longitudinally of the shaft and having a conical surface adapted to enter and expand said spring radially and force it against the washer, and acentrifugal device adapted to move said slidable member into position to expand the spring when the shaft is rotated,,said spring adapted to contract on said conical surface and force said slidable member and the centrifugal device to normal positions when the shaft slows down and before it stops.

6. Circuit controlling means comprising a shaft, a friction disk rotatable about the shaft, a switch operable by said disk, a washer rotatable with the shaft and movable to frictionally engage the disk, an annular helical spring surrounding the shaft adjacent the washer, a member slidable longitudinally of the shaft and having a conical end adapted to enter and expand the spring, a centrifugal device having rocking parts on opposite sides ofthe shaft, and links connecting said parts with said member.

. 7. Circuit controlling means com rising a shaft, a friction disk rotatable a ut the shaft, a switch operable by said disk, a washer rotatable with the shaft and movable to frictionally engage the disk, said shaft having annular groove adjacent the washerfan annular helical spring normally resting infsaid groove, a member slidable longitudinally of the shaft and having a conical end ada ted to lift the sprin out of the groove an expand it against t e washer, and a centrifugal device adapted to force said member toward the washer when the shaft is rotated,

8. Circuit controlling means comprising a shaft, a sleeve secured to the shaft, a frictionmember rotatable about the sleeve, 9. switch operable by said member, a device rotatable with the sleeve and adapted to frictionally engage said member, said sleeve hav ing an annular groove adjacent said device, an annuiar helical spring normaily resting in said groove, a member slidabie on the sleeve and having" a conical end adapted to lift said spring from the groove and expand it against said device, and a centrifugal device mounted on the sleeve and adapted to force said member into said spring when the shaft is rotated' 9. Circuit controlling means comprising a shaft, a friction member rotatable about the shaft, a switch member biased to open position, connections between said members whereby they move together, a device rotatable with the shaft and adapted to frictionally engage said friction member, and centrifugaily operated means adapted to press said device into frictional engagement with said friction member when the shaft is rotated above a certain low speed and to release said device when the shaft slows down and before it stops.

10. Circuit controlling means comprising a shaft, a friction member rotatable about the shaft, a centrally pivoted switch lever, means whereby said lever may be resiliently pressed to either of two positions, an arm connecting said friction member with said lever so that they will move together, a device rotatable with the shaft and adapted to frictionaliy engage said friction member, and centrifugally operated means adapted to press said device into frictional engagement with said friction member when the shaft is rotated above a certain low speed and to release said device when the shaft slows down and before it stops.

In testimony whereof I afiix m signature.

GEORGE H. WHI'ITI GHAM. 

